forming bow rails from stainless tube

Discussion in 'Boatbuilding' started by dick, Feb 12, 2010.

  1. dick
    Joined: Aug 2008
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    dick Junior Member

    Has anyone formed their own bow rails I have 1" stainless steel tube and a tube bender but not a former any Ideas?
  2. northerncat
    Joined: Jan 2007
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    northerncat Senior Member

    yes i have i used a cardboard outline template and just bent until it matched the template, you need a good bender though that doesnt kink or dent the tube
  3. CDK
    Joined: Aug 2007
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    CDK retired engineer

    For such a job I made a tool with 3 profiled wheels or discs, 2 small ones to the left of the tube, a large adjustable one to the right between the small ones.

    With such a setup you can bend a tube gradually over the desired length by adjusting the large disc a tiny bit and feeding the tube through after each adjustment. It takes a lot of time but produces perfect shapes.
  4. Guest62110524

    Guest62110524 Previous Member

    tube or pipe? tube is generally up to 1.6 wall,
    anyways. draw your plan view and then form the tube gently to the plan of say the sheer, with a soft rubber mallet and tube laid on sandbags or soft wood blocks Tap gently along the tube
    when it come to the bends say R= 400 OR WHATEVER you can not bend tube without tube bender which has dies and slipper exact fit to tube
    However if you have pipe , as in 3mm or sched 40 or nipple tube you can do it in a normal pipe bender
  5. Guest62110524

    Guest62110524 Previous Member

    al al is a very cheap way, it is the only metal that has not soared in price
    here Iam bending it, I anneal, smoke the tube with acetalyne til black, turn on oxy, heat til black goes away. quench and bend
    I do this to 2 inch, you can then either leave a is or anodize, wonderful and 3mm wall al al will be stronger than ss tube 1.6
    al al pipe 8 dollars kg, ss 50?
    Last edited: Jun 21, 2010
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  6. alan white
    Joined: Mar 2007
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    alan white Senior Member

    You can usually make smooth bends by packing the tube full of sand and plugging the ends. Tubes filled with sand don't kink because the sand can't compress.
  7. TollyWally
    Joined: Mar 2005
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    TollyWally Senior Member

    Thanks for the input and especially thanks for the pic. I'm a real picture guy, what do they say? a picture's worth a thousand words.

    When you are heating the aluminum to bend it are you running acytelene only in the torch?

    Is the smoke an indicator of heat or something like that or is the carbon from the soot somehow part of the process?

    Is propane hot enough?

    Always nice to learn from a guy whose done it.
  8. Guest62110524

    Guest62110524 Previous Member

    yes the smoke is the guide, propane is hot enough , when you turn on the oxy, with big flame, but keep the tip away from the al al ,
    the comment you made Tolly is really appreciated, I try back everything I do with pics, this [i is of a fuel tank filler, it is a fraction of the cost of rubber hose,
  9. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    If you fill it with sand and cap it, a wooden form will work. You can use blocks to make an outline and bend the tube around them.

  10. Ilan Voyager
    Joined: May 2004
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    Ilan Voyager Senior Member

    On ALUMINUM it's pretty easy. Propane is largely enough for this kind of heating, no need of oxygen, a common torch if big enough will do the job. Use a smooth big flame and be patient.

    The trick of the acetylene smoke gives about 300° Celsius on surface, and about 180° Celsius in the metal. It's the trick used by those welding aluminum with a oxygen-acetylen torch (I'm of those...)
    Other tricks; common white soap it will darken at 240° Celsius. A stick of a light pine wood rubbed on the surface of the hot metal will began to charcoal (blacken) at about 270° Celsius. You have also special markers (Templestick for example) that will change of color at the chosen temperature.

    Aluminum will bend like rubber at 220° Celsius with no cracking, wrinkles or spring back. Filling the tube with fine silica sand (which must be perfectly dry) helps a lot of times on thin walled tubes, but makes the heating and cooling very long.
    A bender makes things easier. You can find it from 120 bucks or make your own like Woosh. I use a very common chinese one with a 16 ton hydraulic jack bought 220 bucks (but I bend a lot of tubes).

    Stainless Steel is a bit different. As the tubes are thin walled and wrinkle fastly, it's better to fill with sand, or use special springs that are put inside if the radius is getting tight. There is no need to heat excepted very tight curves.

    Aluminum in the kind of 6061 is far cheaper than SS, and I find personnaly easier to work and weld than SS. The corrosion resistance is very good with some precautions. And as says Whoosh it's very strong
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